Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 26 The Tree of Life

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Changing Life on a Changing Earth Life is a continuum extending from the earliest organisms to the great variety of species that exist today

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geological events that alter environments – Change the course of biological evolution Conversely, life changes the planet that it inhabits Figure 26.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Conditions on early Earth made the origin of life possible Hypothesis: – Chemical and physical processes on early Earth produced very simple cells through a sequence of stages

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Earth formed ~ 4.6 billion years ago Earth’s early atmosphere – Contained water vapor + many chemicals released by volcanic eruptions – Little or no O 2  reducing atmosphere

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings As material circulated through the apparatus, Miller and Urey periodically collected samples for analysis. They identified a variety of organic molecules, including amino acids such as alanine and glutamic acid that are common in the proteins of organisms. They also found many other amino acids and complex, oily hydrocarbons. RESULTS Figure 26.2 Miller and Urey set up a closed system in their laboratory to simulate conditions thought to have existed on early Earth. A warmed flask of water simulated the primeval sea. The strongly reducing “atmosphere” in the system consisted of H 2, methane CH 4 ), ammonia ( NH 3 ), and water vapor. Sparks were discharged in the synthetic atmosphere to mimic lightning. A condenser cooled the atmosphere, raining water and any dissolved compounds into the miniature sea. EXPERIMENT Electrode Condenser Cooled water containing organic molecules H2OH2O Sample for chemical analysis Cold water Water vapor CH 4 H2H2 NH 3 CONCLUSION Organic molecules, a first step in the origin of life, can form in a strongly reducing atmosphere. Miller – Urey experiment Lab simulations of early Earth atmosphere:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings First organic cmpds. may have formed near submerged volcanoes and deep-sea vents Figure 26.3

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some organic cmpds. may have come from space Carbon cmpds. have been found in some of the meteorites

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Possibly, life is not restricted to Earth

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Abiotic synthesis Small organic molecules – Polymerize when they are concentrated on hot sand, clay, or rock

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protobionts – Aggregates of abiotically produced molecules surrounded by membrane

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protobionts could have formed spontaneously from abiotically produced organic cmpds e.g., small membrane-bounded droplets called liposomes form when lipids are added to water

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 20  m (a)Simple reproduction. This lipo- some is “giving birth” to smaller liposomes (LM). (b)Simple metabolism. If enzymes—in this case, phosphorylase and amylase—are included in the solution from which the droplets self-assemble, some liposomes can carry out simple metabolic reactions and export the products. Glucose-phosphate Phosphorylase Starch Amylase Maltose Phosphate Figure 26.4a, b

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The “RNA World” and the Dawn of Natural Selection The first genetic material – probably RNA, not DNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings RNA molecules (ribozymes) catalyze many different reactions, including – Self-splicing – Making copies of short stretches of their own sequence Figure 26.5 Ribozyme (RNA molecule) Template Nucleotides Complementary RNA copy 3 5 5

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Early protobionts with self-replicating, catalytic RNA – used resources and increased in number through natural selection

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The fossil record chronicles life on Earth Study of fossils – Window into the lives of organisms that existed long ago, information about the evolution of life over billions of years

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fossil dating Sedimentary strata – Reveal the relative ages of fossils

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Index fossils – Similar fossils found in the same strata in different locations – Strata at one location correlates w/ strata f/ another location Figure 26.6

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Absolute ages of fossils – Determined by radiometric dating Figure Accumulating “daughter” isotope Ratio of parent isotope to daughter isotope Remaining “parent” isotope Time (half-lives)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Magnetic reversals of the north and south magnetic poles – Have occurred repeatedly in the past –  record on rocks throughout the world

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geologic record divided into – Three eonsand many eras and periods Time periods – Mark major changes in the composition of fossil species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geologic record Table 26.1

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mass Extinctions – Rapid global environmental changes  a majority of species were swept away Figure 26.8 Cambrian Proterozoic eon Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Paleogene Neogene Number of families ( ) Number of taxonomic families Extinction rate Cretaceous mass extinction Permian mass extinction Millions of years ago Extinction rate ( ) PaleozoicMesozoic ,500 1,500 1, ,000 Ceno- zoic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Major mass extinctions The Permian extinction – Claimed 96% of marine animal species and 8 out of 27 orders of insects – Possibly caused by enormous volcanic eruptions

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cretaceous (KT) extinction – Doomed many marine and terrestrial organisms, notably dinosaurs – Likely/ possibly caused by the impact of a meteor Figure 26.9 NORTH AMERICA Chicxulub crater Yucatán Peninsula

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings After mass extinctions  adaptive radiations into newly vacated ecological niches

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Analogy of a clock – places major events in the Earth’s history in the context of the geological record Figure Land plants Animals Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen Prokaryotes Origin of solar system and Earth Humans Ceno- zoic Meso- zoic Paleozoic Archaean Eon Billions of years ago Proterozoic Eon

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings As prokaryotes evolved, they exploited and changed young Earth Oldest known fossils are stromatolites – Rocklike structures w/ many layers of bacteria and sediment – 3.5 billion years old

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lynn Margulis (top right), of the University of Massachussetts, and Kenneth Nealson, of the University of Southern California, are shown collecting bacterial mats in a Baja California lagoon. The mats are produced by colonies of bacteria that live in environments inhospitable to most other life. A section through a mat (inset) shows layers of sediment that adhere to the sticky bacteria as the bacteria migrate upward. Some bacterial mats form rocklike structures called stromatolites, such as these in Shark Bay, Western Australia. The Shark Bay stromatolites began forming about 3,000 years ago. The inset shows a section through a fossilized stromatolite that is about 3.5 billion years old. (a) (b) Figure 26.11a, b

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prokaryotes were Earth’s sole inhabitants – From 3.5 to about 2 billion years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron transport systems of a variety of types – Essential to early life – Some aspects that possibly precede life itself

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis and the Oxygen Revolution Earliest types of photosynthesis – Did not produce O 2

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxygenic photosynthesis – Evolved ~ 3.5 bya in cyanobacteria Figure 26.12

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings O 2 began to accumulate in the atmosphere ~ 2.7 bya – Challenge for life – Opportunity to gain energy f/ light – Allowed organisms to exploit new ecosystems

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes Question??  how eukaryotic cells evolved from much simpler prokaryotes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oldest fossils of eukaryotic cells – 2.1 billion years

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosymbiosis – Mitochondria and plastids were formerly small prokaryotes living within larger host cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Probably undigested prey or internal parasites Figure Cytoplasm DNA Plasma membrane Ancestral prokaryote Infolding of plasma membrane Endoplasmic reticulum Nuclear envelope Nucleus Engulfing of aerobic heterotrophic prokaryote Cell with nucleus and endomembrane system Mitochondrion Ancestral heterotrophic eukaryote Plastid Mitochondrion Engulfing of photosynthetic prokaryote in some cells Ancestral Photosynthetic eukaryote

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eventually host and endosymbionts would have become a single organism

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Supporting evidence: – Similar inner membrane structures and functions – Both have their own circular DNA (genes) – Own ribosomes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic Cells as Genetic Chimeras Additional endosymbiotic events and horizontal gene transfers –  large genomes and complex structures

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic flagella and cilia – May have evolved f/ symbiotic bacteria, Figure  m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Multicellularity evolved several times

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molecular clocks date the common ancestor of multicellular eukaryotes to 1.5 billion years Oldest known fossils of eukaryotes ~ 1.2 bya

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chinese paleontologists recently described 570-million-year-old fossils – probably animal embryos Figure 26.15a, b 150  m 200  m (a) Two-cell stage (b) Later stage

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The first multicellular organisms were colonies – Collections of autonomously replicating cells Figure  m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some cells in the colonies – Became specialized for different functions The first cellular specializations – Had already appeared in the prokaryotic world

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The “Cambrian Explosion” Most of the major phyla of animals – Appear ‘suddenly’ in the fossil record that was laid down during the first 20 million years of the Cambrian period

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 animal phyla, Cnidaria and Porifera – Are older, dating from the late Proterozoic Figure Early Paleozoic era (Cambrian period) Millions of years ago Late Proterozoic eon Sponges Cnidarians Echinoderms Chordates Brachiopods Annelids Molluscs Arthropods

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Molecular evidence – Suggests that many animal phyla originated and began to diverge much earlier, between 1 billion and 700 million years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Plants, fungi, and animals – Colonized land about 500 million years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Symbiotic relationships between plants and fungi – Are common today and date from this time

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Continental Drift Earth’s continents are not fixed – They drift across our planet’s surface on great plates of crust that float on the hot underlying mantle

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Often, these plates slide along the boundary of other plates – Pulling apart or pushing against each other Figure North American Plate Caribbean Plate Juan de Fuca Plate Cocos Plate Pacific Plate Nazca Plate South American Plate African Plate Scotia Plate Antarctic Plate Arabian Plate Eurasian Plate Philippine Plate Indian Plate Australian Plate

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many important geological processes – Occur at plate boundaries or at weak points in the plates themselves Volcanoes and volcanic islands Trench Oceanic ridge Oceanic crust Seafloor spreading Subduction zone Figure 26.19

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The formation of the supercontinent Pangaea during the late Paleozoic era – And its breakup during the Mesozoic era explain many biogeographic puzzles Figure India collided with Eurasia just 10 million years ago, forming the Himalayas, the tallest and youngest of Earth’s major mountain ranges. The continents continue to drift. By the end of the Mesozoic, Laurasia and Gondwana separated into the present-day continents. By the mid-Mesozoic, Pangaea split into northern (Laurasia) and southern (Gondwana) landmasses. Cenozoic North America Eurasia Africa South America India Madagascar Antarctica Australia Laurasia Mesozoic Gondwana At the end of the Paleozoic, all of Earth’s landmasses were joined in the supercontinent Pangaea. Pangaea Paleozoic Millions of years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings New information has revised our understanding of the tree of life e.g. Molecular (e.g. DNA, protein) Data – insights to deepest branches of the tree of life

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Early classification systems had two kingdoms – Plants and animals

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Robert Whittaker’s system with five kingdoms – Monera, Protista, Plantae, Fungi, and Animalia Figure PlantaeFungiAnimalia Protista Monera Eukaryotes Prokaryotes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reconstructing the Tree of Life: A Work in Progress A three domain system – Has replaced the five kingdom system – Includes the domains Archaea, Bacteria, and Eukarya Each domain – Has been split by taxonomists into many kingdoms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One current view of biological diversity Figure Proteobacteria Chlamydias Spirochetes Cyanobacteria Gram-positive bacteria Korarchaeotes Euryarchaeotes, crenarchaeotes, nanoarchaeotes Diplomonads, parabasalids Euglenozoans Alveolates (dinoflagellates, apicomplexans, ciliates) Stramenopiles (water molds, diatoms, golden algae, brown algae) Cercozoans, radiolarians Red algae Chlorophytes Charophyceans Domain Archaea Domain Eukarya Universal ancestor Domain Bacteria Chapter 27 Chapter 28

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bryophytes (mosses, liverworts, hornworts) Plants Fungi Animals Seedless vascular plants (ferns) Gymnosperms Angiosperms Amoebozoans (amoebas, slime molds) Chytrids Zygote fungi Arbuscular mycorrhizal fungi Sac fungi Club fungi Choanoflagellates Sponges Cnidarians (jellies, coral) Bilaterally symmetrical animals (annelids, arthropods, molluscs, echinoderms, vertebrates) Chapter 29 Chapter 30 Chapter 28Chapter 31Chapter 32Chapters Figure 26.21